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Blue light comprises the electromagnetic spectrum between approximately 380-500 nm. The sun is the main source of blue light, although we also receive emissions of this type of light by electronic devices and artificial lighting. Changes in lighting systems and lifestyle habits have led to the questioning of exposure to blue light emitted by artificial sources as a possible health problem. Faced with this potential problem, ophthalmic lens laboratories brought to market lenses with specific treatment against hazard blue light emitted by electronic devices. In this work we measure the spectral transmittance of 6 blue filter ophthalmic lenses from 4 different laboratories, Essilor, Hoya, Shamir and Kodak. We face the transmission spectra measured with the emission spectra of 3 different electronic devices, to be able to discuss the suitability of these blue filter lenses for use with electronic devices. We conclude that the transmittance of blue filters in the maximum blue light emission range is high above 90%, and that changing the correlated color temperature of electronic devices results in a greater reduction in exposure to hazard blue light. We also found that Shamir's Blue Zero and Essilor's Eye Protect System lenses block UVA light and have low transmittance in the range of 380- 420 nm, so they would be more effective for protection against blue light outdoors than for use with electronic devices.

In this paper, data transmission using a white LED and blue filter is demonstrated. The conventional white LEDs are produced by combining blue LEDs with yellow phosphor coating. This combination generates white light. However, the yellow phosphor coating has bandwidth limiting effect. As a result, the data rate of the transmission is limited. One of the method that can be used to cope this effect is by employing blue filter at the receiver. This method filters out the yellow components. To test the method, an experimental SoC-based test-bed using a HW/SW co-design approach is developed.

2nd International Conference on Advanced Communication Technologies and Networking, CommNet 2019 -- 12 April 2019 through 14 April 2019 -- -- 148920 This paper proposes a means to maximize the data rate supported by a visible light communication (VLC) system. The investigated VLC system uses phosphor-coated white light emitting diodes (LEDs), which are common in existing illumination systems but are also known to limit the communication system's data rate. In this paper, we propose a remedy to such a limitation by adding a response-flattening filter at the receiver's end to mitigate the effect of the slow yellow phosphor spectral component. An experimental study is conducted to evaluate the validity of the proposed remedy. The resulting performance is compared with an existing remedy that involves adding a blue filter at the receiver. Off-the-shelf commercial filters are used in the experiment. Enhanced bit-error-rates (BERs) and signal-to-noise ratios (SNRs) at high data rates are observed. Specifically, our experimental work demonstrates that BER is enhanced by 40% and 15% for data rates up to 12 Mbps when responseflattenina filter and blue filter are adopted, respectively. © 2019 IEEE.

16th International Multi-Conference on Systems, Signals and Devices, SSD 2019 -- 21 March 2019 through 24 March 2019 -- -- 154292 This paper experimentally evaluates the performance of visible light communications (VLC) systems employing phosphor-coated white light emitting diodes (LEDs). Phosphor-coated white LEDs though widely used commercially, are known to limit the system's maximum data rate. Such a limitation is conventionally treated by two methods: either adding a blue filter at the receiver or using orthogonal frequency multiplexing (OFDM) digital modulation technique. Adding a blue filter at the receiver is controversial in current literature and claimed to decrease the signal-to-noise-ratio (SNR) or to be inefficient if OFDM is employed. Hence, in this work, we experimentally evaluate the above OFDM based VLC system with and without a blue filter. Results are compared to prove that adding a blue filter at the receiver boosts SNR and bit-error-rate (BER) values. This, in turn, helps maximize the data rates supported by such systems. The addition of a blue filter is tested with different modulation techniques. Results in this work remove the controversy around employing a blue filter in OFDM based VLC systems with phosphor-coated white LEDs. Improved BERs and SNRs at high data rates are observed. Specifically, this experimental work demonstrates a BER enhancement of ?40% and ?15% for data rates up to 12 Mbps when a blue filter is added. © 2019 IEEE. Texas A and M University, TAMU: 2019 -- insignificant effect if OFDM is employed. In this work, we experimentally assess the above OFDM based VLC system with and without adding a blue filter. Comparing results prove that adding a blue filter at the receiver’s end improves BER values by ?35% to ?47% according to the modulation type used. Results from this work show the following: • It removes the doubts that blue filters neg-atively affect the SNR. Despite reducing the signal power by suppressing the slow yellow spectrum, blue filters reject ambient noise in the visible spectra. Thus, the resulting SNR is elevated. • Blue filters continue to boost the system’s per-formance in terms of SNR and BER in VLC systems employing OFDM. Hence, the claim that blue filters maybe of no use while using OFDM is proven wrong. • Combining adding a blue filter along with adopting OFDM results in improved BERs and SNRs at high data rates. In specific, this experimental work depicts a BER reduction of 40% and 15% for data rates up to 12 Mbps when a blue filter is added with the presence of OFDM modulation. ACKNOWLEDGEMENTS This work was supported by the Texas A&M University at Qatar (TAMUQ) responsive research seed grants 2019. --

A novel interacting multiple model based on BLUE filter (IMM-BLUE) for tracking a maneuvering target using radar/ESM heterogeneous sensors is presented in this paper. Under the architecture of the proposed algorithm, the interacting multiple model (IMM) deals with the model switching, while the BLUE filter accounts for non-linearity in the dynamic system models. The simulation results show that the presented IMM-BLUE has higher tracking precision than the IMM-DCM, and IMM-EKF.

This paper presents an extended BLUE filter with Pitot tube and windspeed measurements. Though widely used in aviation, Pitot tube is ignored by scholars because it only measures the speed of an aircraft relative to the air. Investigation shows the linear combination of Pitot tube and windspeed measurements can yield aircraft velocity estimation to improve performance. After a thorough analysis of the relationship between measurements and target state, an extended BLUE filter model is built, filter parameters are derived. Extensive simulation comparisons with other state-of-the-art methods verify the proposed method is accurate and computationally efficient.

For an indoor Visible Light Communication system with phosphorescent LEDs, we show a blue receive filter is particularly suitable for cool-white LEDs but less attractive for warm-white LEDs. Distance and sunlight also influence whether a blue filter should be used.

We propose a multi-band OFDM modulation for wireless VLC system together with dynamic bandwidth allocation. In addition, the proposed modulation format also can enhance the maximum VLC traffic rate to 17.8% without using blue filter.

Introduction Virtual chromoendoscopy is used to enhance surface patterns and colour differences. One type of virtual chromoendoscopy is the Fuji Intelligent Colour Enhancement (FICE). Although widely applied in conventional endoscopy, data on FICE application in capsule endoscopy are limited. Furthermore, the validity of Blue filter (feature of RAPID® software) has not been examined. Aim/s We aimed to qualitatively evaluate the use of FICE and Blue filter enhancement, in images of lesions obtained during small bowel capsule endoscopy, comparing them with similar, conventional (white light) images. Methods A total of 167 images (6 different lesion categories) obtained from 200 capsule endoscopy examinations. Two gastroenterologists examined the images with white light, FICE and Blue filter in regards to the visibility of blood vessels, the contrast of the mucosal surface, and the demarcation of lesion borders. The agreed scores were: improved, similar, worse. Inter-observer agreement was calculated. Results For all lesion categories, Blue filter provided image improvement (compared to white light) in 83%, (inter-observer agreement: 0.786). With FICE 1, improvement was observed in 34%, worse image in 55.9%, (inter-observer agreement: 0.646). With FICE 2, improvement was observed in 8.6%, worse in 77.5%, (inter-observer agreement: 0.617). With FICE 3, improvement was seen in 7.7%, worse in 79.9% (inter-observer agreement: 0.669). Conclusion Comparing with FICE, Blue filter offers better image enhancement in capsule endoscopy.

We have obtained imaging polarimetry of the comet C/2013 R1 (Lovejoy) with 2-Channel-Focal-Reducer Rozhen instrument at 2m Ritchey-Chr\'etien-Coud\'e telescope of the Bulgarian National Astronomical Observatory Rozhen in two dust continuum filters covering wavelength intervals clear from molecular emissions and centred at $4430\AA$ in (blue filter) and at $6840\AA$ in (red filter). In imaging mode we measured the degree of linear polarisation $17.01\pm0.09$% in the blue and $18.81\pm0.02$% in the red, which is in a very good agreement with measurements of other comets at the similar phase angle. We have also obtained polarisation maps in both filters. We found a strong correlation between the spatial distribution of the polarisation and the dust colour. Spectropolarimetry of the nucleus region shows an increase of the polarisation with wavelength, and a depolarisation in the spectral regions with gas emission lines, most noticeable in C$_2$ emission band, which shows a polarisation of $6.0\pm1.1$%., Comment: 6 pages, 8 figures, ACM2014 conference proceedings

Visible light communications typically uses a white LED as a data source. Most white LEDs use a slow yellow phosphor combined with a blue LED that has a faster response. An optical filter is often used to remove the slow yellow light before detection. However the need for, and effectiveness of, blue filtering is highly dependent on practical factors such as illumination level, optics gain, and receiver noise characteristics. In this paper, we model a simple indoor Visible light communication environment, and then investigate the effect of blue filtering, and how an optimum blue filter might be chosen.

A technique for improving the reliability of observation by students of partially or completely polarized light with the naked eye is reported. Along with application a polarizing film, it includes the application of a blue filter first suggested by G G Stokes and a pair of theatre binoculars.

We have designed and fabricated the low-polarizing X-plate to increase the luminous throughput for LED projector. We calculate reflectivity characteristic of X-plate as a function of the wavelength at different angles of incidence from air of unpolarized light. A new way to design filter to control the title effect of thin film filters. The wavelength shift of the new design for reflected red filter and reflected blue filter at the angle of 45° ± 8° is 16 nm and 14 nm, respectively.

Excerpt Color constancy is a visual phenomenon wherein colors of objects remain relatively the same under changing illumination. A red apple gives the same red appearance under either a fluorescent or incandescent lamp, although the lights that the apple reflects to the eye are quite different. The light reflected from an object into the human visual pathway is proportional to the product of the illumination incident on the surface and the invariant spectral reflectance properties of the object. The fact that humans possess approximate color constancy indicates that our visual system does attempt to recover a description of the invariant spectral reflectance properties of the object. Often, color constancy and chromatic adaptation are used interchangeably. However, Brill and West seem to suggest otherwise. Using Hunt's demonstration: a yellow cushion looks yellow when the whole scene is covered by a blue filter, but the cushion looks green when it is covered by the blue filter cut to the exact shape of the cushion. They stated that the yellowness of the cushion in the first instance is seen immediately despite the bluish cast of the whole slide; then the bluish cast diminishes after several seconds of chromatic adaptation. The difference in time dependence suggests that chromatic adaptation may be a different phenomenon from color constancy.

AIM: To evaluate whether virtual chromoendoscopy can improve the delineation of small bowel lesions previously detected by conventional white light small bowel capsule endoscopy (SBCE). METHODS: Retrospective single center study. One hundred lesions selected from forty-nine consecutive conventional white light SBCE (SBCE-WL) examinations were included. Lesions were reviewed at three Flexible Spectral Imaging Color Enhancement (FICE) settings and Blue Filter (BF) by two gastroenterologists with experience in SBCE, blinded to each other’s findings, who ranked the quality of delineation as better, equivalent or worse than conventional SBCE-WL. Inter-observer percentage of agreement was determined and analyzed with Fleiss Kappa (k) coefficient. Lesions selected for the study included angioectasias (n = 39), ulcers/erosions (n = 49) and villous edema/atrophy (n = 12). RESULTS: Overall, the delineation of lesions was improved in 77% of cases with FICE 1, 74% with FICE 2, 41% with FICE 3 and 39% with the BF, with a percentage of agreement between investigators of 89% (k = 0.833), 85% (k = 0.764), 66% (k = 0.486) and 79% (k = 0.593), respectively. FICE 1 improved the delineation of 97.4% of angioectasias, 63.3% of ulcers/erosions and 66.7% of villous edema/atrophy with a percentage of agreement of 97.4% (k = 0.910), 81.6% (k = 0.714) and 91.7% (k = 0.815), respectively. FICE 2 improved the delineation of 97.4% of angioectasias, 57.1% of ulcers/erosions and 66.7% of villous edema/atrophy, with a percentage of agreement of 89.7% (k = 0.802), 79,6% (k = 0.703) and 91.7% (k = 0.815), respectively. FICE 3 improved the delineation of 46.2% of angioectasias, 24.5% of ulcers/erosions and none of the cases of villous edema/atrophy, with a percentage of agreement of 53.8% [k = not available (NA)], 75.5% (k = NA) and 66.7% (k = 0.304), respectively. The BF improved the delineation of 15.4% of angioectasias, 61.2% of ulcers/ erosions and 25% of villous edema/atrophy, with a percentage of agreement of 76.9% (k = 0.558), 81.6% (k = 0.570) and 25.0% (k = NA), respectively. CONCLUSION: Virtual chromoendoscopy can improve the delineation of angioectasias, ulcers/erosions and villous edema/atrophy detected by SBCE, with almost perfect interobserver agreement for FICE 1.

tip of the tonometer prism only when the to­ nometer prism is almost fully pushed into the body of the tonometer by contact with the patient's eye. Additionally, the cobalt-blue fil­ ters covering the light sources are easily dis­ lodged, further reducing the amount of blue light to excite fluorescence. In clinical use the illumination of the tonometer is so dim that the room lights must be dimmed in order to use the instrument.1 The poor illumination of the to­ nometer head may produce hypofluorescence of the fluorescein in the precorneal tear film, causing underestimation of the intraocular pressure.2"4 One of us (R.S.) modified the Mark II model of Perkins tonometer to provide substantially increased illumination of the tonometer head. The two 2.7 May lights that usually illuminate the tonometer head were replaced with two Welch-Allyn 3100 halogen bulbs. Blue filter caps to cover the halogen bulbs were fashioned from aluminum tubing and the same type of blue filter as the Perkins tonometer (Eastman Kodak Wratten 47B). The angle of the light sources was unchanged from the original de­ sign. This modification is shown in the Figure. A widening of the case at the site of the exit of the halogen bulbs was made to accommodate the increased diameter of the new light sources. The two 1.35-V mercury cells or four 1.5 V AA batteries that normally power the Perkins to­ nometer were replaced by a 3.5-V Welch-Allyn nickel-cadmium battery to match the voltage of the halogen bulbs. With these modifications the brightness of the illumination of the tonometer head is mark­ edly increased. The fluorescent ring produced by tonometer-corneal contact is easily seen without dimming the room lights and is bright­ er than that seen by using a slit-lamp mounted tonometer. The tonometer head position has less of an effect on the brightness of the fluores­ cent rings. These changes eliminate underillumination of the tonometer prism and minimize any underestimation of the intraocular pres­ sure, that might occur from underillumination, making the Perkins tonometer easier to use and more accurate.

In order to make visible or to photograph structural details of algal chromatophores, an “absorption image” should be produced in the microscope by using a proper light filter. For a number of reasons, this can be done, not by using a red filter whose color is complementary to the green component of the plastid pigments, but by applying a blue filter, complementary to the yellow of both chlorophyll and of carotenoid pigments. The use of Wratten Filter no. 48 is especially recommended for this purpose. Some problems in the use of filters in microscopy are briefly discussed.

A glass filter is described which enables the colour temperature of lamps to be measured, using standard lamps which operate at lower colour-temperatures. The filter is yellow in colour and made from Corning 346 and 507 glasses. The method of construction is described. Colour-temperature measurements made with the glass filter agree to 4°k. with those using the blue liquid filter previously used at the laboratory. The advantages of the yellow filter over the blue filter are that the yellow filter is more stable, the colour-matching properties are better, the energy match is better for a colour match, the temperature coefficient is a fifth of that of the blue filter, and the yellow filter is placed in front of the brighter lamp, so that, for a colour match, the lamps are nearly equidistant from the photometer. The properties of glass filters made from (a) a yellow glass with Zeiss U.G.3, (b) Corning 346 with Chance O.V.2, and (c) Cobalt blue glass are mentioned.

An observation of the corona during the 7 March, 1970 eclipse through a Wollaston prism-red and blue filter combination was carried out for the purpose of confirming the prediction that the component of the K-corona with electric vector radial to the Sun is redder than the tangential component. An analysis of a portion of the resulting data seems to confirm this prediction, and also indicates that the method is useful for determining the three-dimensional configuration of the very inner corona. A three-dimensional configuration is suggested for a portion of the NE quadrant of the Sun, including the large NE streamer and an adjacent low-lying loop.

Following a stroke or serious injury to the spinal cord leading to paraplegia, the lower motoneurones are not capable of being driven by the upper motoneurones. A scheme is suggested by which it could be possible to drive such lower motoneurones by controlled and patterned stimuli leading to meaningful and coordinated limb movements. This review suggests that a red dye could be injected into an extensor muscle, and this dye would be taken up by the nerve ending and transported retrogradely to the motoneurones. A blue dye could be injected into the flexor muscle and this would be taken up by the nerve terminals and transported to the motoneurones. In this way the extensor motoneurones in the spinal would contain a red dye and the flexor motoneurones would contain a blue dye. The dyes chosen would be photoactive and light shone on them would depolarize the nerve cells and set up action potentials, which would make the muscle contract. The light would come from a 1 mm fibre optic guide containing many optic fibres. These would be driven by two controlled xenon flash lamps. One would lead through a blue filter to 50% of the optic fibres, whilst the other lamp would go via a red filter to the other 50% of the optic fibres. A micro-circuit would control the xenon flash patterns so that as a patterned series of pulses, stimulated the flexor motoneurones the extensory motoneurones would be switched off. The advantage of light fibre stimulation is that it would be relatively insensitive to movement and not require accurate location; so long as the light path included the motor neurones, it would be possible to selectively drive neurones within the nerve cord.

Details are given concerning the components used in constructing a photoelectric spectrophotometer employing as light-sensitive element a vacuum emission photocell of a modern type with central plate cathode. It is claimed that the instrument as a whole has a linear response over the necessary range of photocurrents and the method by which this property was tested is described. The instrument has been applied to the measurement of spectral transmissions of the International Standard Blue Filter R 3.28 and the results, which are in good agreement with the internationally adopted figures, are given in full. The effect of temperature on this filter is shown also.